1. Field of the Invention:
This invention relates to a loading dock signal and control system and more particularly to a system which achieves a very high degree of safety and security in the parking of vehicles at a dock and in the loading and unloading of the vehicles. The system of the invention is readily installed and is easily adaptable for use with various types of associated apparatus including levelers, door openers, security systems, monitoring systems and control systems. It is also highly reliable but is also easy to trouble-shoot should any problems occur and it is readily and economically manufacturable.
2. Background of the Prior Art:
The Hahn U.S. Pat. No. 4,692,755, issued Sept. 8, 1987 discloses a loading dock signal and control system which has important advantages over prior system, particularly with respect to increased safety and reliability. The Hahn system is operative with a locking device which is mounted on a loading dock and which includes a hook moved upwardly to lockingly engage a safety bar of a vehicle and restrain the vehicle against movement relative to the dock while being loaded or unloaded. The system includes outside red and green lights for indicating to a truck driver when it is not safe and safe to back in or pull out and inside red and green lights for indicating to dock attendants when it is not safe and safe to load or unload a docket truck or trailer. An important safety feature of the system is in the provision of a slippage control mode of operation in which the hook, after being moved to its upper lock position, is automatically moved upwardly thereto whenever it has slipped to a position below the lock position. The system is also advantageous in detecting malfunctions and generating alarm signals in response thereto.